There has been known a conventional objective lens supporting mechanism employed in an optical lens actuator for an optical disc apparatus as shown in FIG. 1 (Prior Art).
The objective lens supporting mechanism shown in FIG. 1 is provided with an objective lens holder 22 for holding thereon an objective lens 21, a pair of parallel leaf springs 23 for supporting the lens holder 22 in a tracking direction y and a pair of parallel leaf springs 24 for supporting the lens holder 22 in a focusing direction z. The supporting mechanism is further provided with a supporting base for supporting a base end of the leaf springs 24, a focusing coil 26 and a tracking coil 27. In FIG. 1 (Prior Art), an arrow x directs a longitudinal axis of the actuator, arrow y directs a tracking direction and arrow z directs an optical axis of the objective lens that is a focusing direction.
Further, there has been known another conventional objective lens supporting mechanism in which the objective lens holder is supported by four suspension wires instead of leaf springs and the like.
The conventional objective lens supporting mechanisms described above would raise a problem that a rolling of the lens holder easily occurs because of unbalance in weight of the movable parts, unbalance in left and right directions of electromagnetic forces during focusing or tracking actuations. For example, as shown in FIG. 2 (Prior Art), two forces a and b directly opposite to each other are applied to the leaf springs 23 for supporting the lens holder 22 in the tracking direction y. The two forces act as a distorting force on the leaf springs 23 since ore force does not suppress the other. Therefore, the movable part would be distorted and vibrated along the direction x as shown in arrow c in FIG. 2 (Prior Art), also thereby deforming an optical axis z of the objective lens 21. In FIG. 2 (Prior Art), the upper side is a free end (facing the objective lens holder) side while the lower side is a fixed end side.